Given, for example, legislation arising from the global warming problem, there are demands for strengthened control of the quantity of energy used in factories and manufacturing lines. Because heat-producing equipment and air-conditioning equipment are facilities equipment that can consume a particularly large quantity of electricity, often the upper limit for the quantity of energy consumed is controlled so as to be kept lower than the maximum value in conventional equipment. For example, in facilities equipment that runs on electric power, the operations are performed in particular so that the quantity of electricity used will be within specific limitations prescribed by an electric power demand controlling system.
In particular, there have been proposals for methods, using, for example, a total power suppression control device, for limiting the total quantity of electric power that is supplied simultaneously at the time of startup in heat-producing equipment that is provided with a plurality of electric heaters (when heating up simultaneously the temperature in multiple areas wherein electric heaters are installed). See, for example, Japanese Unexamined Patent Application Publication No. 2012-048533 (the “JP '533”). FIG. 8 is a block diagram illustrating the structure of a conventional heated device disclosed in the JP '533. The heating device comprises: a heat treatment furnace 100 for heating an object to be heated; heaters H1 through H4, which are a plurality of control actuators disposed within the heat treatment furnace 100; a plurality of temperature sensors S1 through S4 that measure the temperatures of regions that are heated by the respective heaters H1 through H4; a total electric power limiting/controlling device higher-level controlling portion 101 for calculating the manipulated variables MV1 through MV4 from the outputs of the heaters H1 through the H4; a total electric power limiting/controlling device lower-level controlling portion 102; and electric power regulators 103-1 through 103-4, for providing to the respective heaters H1 through H4, electric power in accordance with the manipulated variables MV1 through MV4 that are outputted from the total electric power limiting/controlling device 102.
The higher-level controlling portion 101 of the total electric power limiting controlling device receives, from a higher-level PC 104, which is a computer of the electric power demand controlling system that controls the electric power, information regarding the total allocated power PW that regulates the amount of electric power used by the heaters H1 through H4, and then calculates the total electric power used TW, which is the total of the electric powers used by the individual heaters H1 through H4, and calculates manipulated variable upper limit values OH1_1 through OH1_4 for the individual control loops so that the total electric power used TW does not exceed the total allocated electric power PW.
The lower-level controlling portion 102 of the total power limiting/controlling device is structured from temperature regulators C1 through C4, which are structured from a plurality of control loops Ri (where i=1 through n), where, in the example in FIG. 8, the number n control loops is n=4. The individual temperature regulators C1 through C4 each calculate the respective manipulated variables MV1 through MV4, through, for example, PID control calculations, and execute upper limit limiting processes so as to control the manipulated variables MV1 through MV4 so as to be no higher than the manipulated variable upper limit value OH1_1 through OH1_4, and then output, to the electric power regulators 103-1 through 103-4 of the corresponding control loops, the manipulated variables MV1 through MV4 after the upper limit processing. The control of the total power is achieved through manipulating the manipulated variable upper limit value OH1_1 through OH1_4 of the temperature regulators C1 through C4 in this way.
In the total electric power limiting/control disclosed in the JP '533, an ordinary temperature controller can be used as the lower-level controlling portion 102. That is, this is an easy approach at instrumentation for the device manufacturer. Moreover, there is no limit to only a manipulated variable upper limit value OH, but rather many different customized controls can be produced through operations for setting appropriately the manipulated variable lower limit value OL in a lower-level controlling portion 102 from a higher-level controlling portion 101.
Note that the manipulated variable lower limit value OL and the manipulated variable upper limit value OH are sent through a communication function from the higher-level controlling portion 101 to the lower-level controlling portion 102. In this case, if, after a value that is higher than normal or a value that is lower than normal is set temporarily, as the manipulated variable lower limit value OL or the manipulated variable upper limit value OH, from the higher-level controlling portion 101 and a fault occurs in the communication function prior to the value being returned to the normal value, this may cause the manipulated variable lower limit value OL or the manipulated variable upper limit value OH to remain, over an extended period of time, at a value that is larger than the normal value or a value that is smaller than the normal value. This type of unanticipated setting can produce major malfunctions in control, or other problems.
For example, let us assume that the manipulated variable upper limit value OH calculating algorithm for the total electric power suppression control disclosed in the JP '533 were executed in the higher-level controlling portion 101, and calculated manipulated variable upper limit value OH were sent continuously to the lower-level controlling portion 102 (the temperature regulator) through a communication function. FIG. 9 (A) and FIG. 9 (B) will be used to explain the problems that occur when the manipulated variable upper limit value OH is locked in for an unanticipated long period of time due to a fault in the communication function that ties together the higher-level controlling portion 101 and the temperature regulator at this time. FIG. 9 (A) illustrates the change in a process variable PV (which, in the example in FIG. 8, is a temperature measurement value), and FIG. 9 (B) illustrates the change in the manipulated variable MV.
Let us assume that, for convenience in the distribution of electric power, the manipulated variable upper limit value OH is changed, temporarily, from 100% to 20% at a time t1 for the temperature regulator of a PID control loop wherein there is no call for increasing the temperature (that is, for a temperature regulator wherein the temperature setting value SP has been changed from 300° C. to 150° C., as shown in FIG. 9 (A)). If, at this point, a fault were to occur in the communication function when the manipulated variable upper limit value OH has been set to 20%, then despite the actual need for the manipulated variable upper limit value to be returned to OH=100%, as illustrated by the dotted line 130, in the temperature regulator the manipulated variable upper limit value OH will remain set at 20%. Given this, if the communication fault is not resolved, then when, at time t2, when the temperature setting value SP for this temperature regulator is changed from 150° C. to 300° C. to begin increasing the temperature, the manipulated variable upper limit value OH will still be set to 20%, so that, at time t2 and beyond, a serious deficiency in the heating performance will occur, which will tie into major problems in terms of the operating state of the heating device.
Conversely, let us assume that, for example, some sort of specialty algorithm is executed by the higher-level controlling portion 101, to sequentially set manipulated variable lower limit values OL in the lower-level controlling portion 102 (a temperature regulator) through a communication function. FIG. 10 (A) and FIG. 10 (B) will be used to explain the problems that occur when the manipulated variable lower limit value OL is locked in for an unanticipated long period of time due to a fault in the communication function that ties together the higher-level controlling portion 101 and the temperature regulator at this time. FIG. 10 (A) illustrates the change in a process variable PV (a temperature measurement value), and FIG. 10 (B) illustrates the change in the manipulated variable MV.
At time t3, the temperature setting value SP is changed from 150° C. to 300° C., and, in response, at time t4, the manipulated variable lower limit value OL is changed temporarily from 0% to 80% for the temperature regulator that is the subject in order to force a rapid increase in temperature. If, at this point, a fault were to occur in the communication function when the manipulated variable lower limit value OL has been set to 80%, then despite the actual need for the manipulated variable lower limit value to be returned to OL=0%, as illustrated by the dotted line 140, in the temperature regulator the manipulated variable lower limit value OH will remain set at 80%. Given this, if the communication fault is not resolved, then the process variable PV of the temperature regulator will rise rapidly, and even after reaching a stage wherein there should be a transition to a high temperature maintenance state at time t5, the manipulated variable lower limit value OL will remain set at 80%, preventing the transition to the maintenance state after time t5, which would produce a dangerous temperature overage.
In this way, there is a problem in that, when a specialized processing technology wherein the settings for the manipulated variable lower limit value OL and the manipulated variable upper limit value OH that are used in a lower-level device are set is achieved through a communication function between the higher-level device and the lower-level device, if the manipulated variable lower limit value OL or the manipulated variable upper limit value OH is unexpectedly locked in due to a failure in the communication function, this can lead to a serious or dangerous malfunction. The total electric power limiting control disclosed in the JP '533 is a typical example of a control solution that uses a manipulated variable lower limit value OL and a manipulated variable upper limit value OH, and the problem described above is a problem that is common to this type of control solution.
The present invention was created in order to solve the problem set forth above, and the object thereof is to provide a controlling device and controlling method able to mitigate the problems when a fault occurs in the communication function when a control solution wherein an operation is performed through communication from a higher-level device to set a manipulated variable upper limit value and/or a manipulated variable lower limit value.